This invention is directed to molding compositions comprising ternary blends of a polyetherimide, a polyphthalate carbonate and rubber modified vinyl aromatic polymer.
Polyetherimides resins are well known in the art and are of considerable commercial value for use in molding compositions because of their excellent physical, chemical and thermal properties. The high glass transition and heat deflection temperatures exhibited by these polymers permit their use in high performance applications previously reserved for metals and some thermoset resins. While polyetherimides are known to possess a number of excellent properties, for many applications, it would be desirable to have a resin with improved flexural properties, yet which maintains the toughness and other advantageous physical properties of polyetherimides.
It is known that the flexural properties of polyetherimides can be improved by forming blends of those polymers with a rubber modified vinyl aromatic polymer. See, Giles et al., U.S. Pat. No. 4,393,168. Although such blends maintain many of the physical properties of polyetherimides, they have not been found to have the toughness or impact strengths characteristic of polyetherimides.
Binary blends of polyestercarbonate resins and polyetherimides have been prepared for the primary purpose of improving the thermal properties of the polyestercarbonates. See, pending U.S. patent application Ser. No. 073,319, filed July 13, 1987 and U.S. Pat. No. 4,430,484. Again, although these blends exhibit certain advantageous properties, they have not been found to possess the toughness or impact properties of polyetherimides.
Thus, there exists a need for a polymer blend which has good thermal properties and improved flexural properties over polyetherimides, yet maintains the toughness and impact properties of those polymers.